The present invention relates to a car headlamp, and more particularly to a car headlamp in which a discharge-type bulb is employed as a light source.
Recently, discharge-type bulbs having been employed in automotive lamps in view of their good luminous efficiency and desirable color spectrum, as well as their long service life. However, a metal halide bulb, which is a common type of discharge bulb, produces a large quantity of ultraviolet rays together with visual light rays from the discharge which takes place in the gases (mercury gas, iodide gas and xenon gas) contained in the discharge space of the lamp. Ultraviolet rays in a wavelength range of 240-290 nm are believed capable of destroying protein molecules, ultraviolet rays in a wavelength range of 290-320 nm are believed a cause of skin cancer, and ultraviolet rays in a wavelength range of 369-370 nm destroy resin materials. Thus, there has been a problem that the light output of the discharge bulb includes health-damaging ultraviolet rays so that it is undesirable to be subjected to illumination for long periods from such a lamp. Also, resin members in the vicinity of the discharge bulb tend to deteriorate rapidly.
To cut off the emission of ultraviolet rays from a headlamp, it has been proposed to use a front lens made of a glass material which blocks the transmission of ultraviolet rays. If the front lens is broken, however, there is a problem that ultraviolet rays will be emitted.